Haemangiopericytoma / Solitary Fibrous tumour (HPC-SFT)
What is a haemangiopericytoma/solitary fibrous tumour (HPC-SFT)?
When viewed under a microscope the appearance of haemangiopericytomas and solitary fibrous tumours are quite different, so the two names have been kept when referring to tumours of the central nervous system (which consists of the brain and spinal cord). However, when these tumours are studied in a laboratory similar genetic patterns can be seen and hence they are classified as one tumour type but with 3 distinct grades.
HPC-SFTs are categorised as a type of mesenchymal tumour, a category that includes a wide variety of benign and malignant tumours that can appear anywhere throughout the body in soft tissue and bone. Cancerous forms of mesenchymal tumours may also be referred to as sarcomas.
Mesenchymal tumours originate from cells that should normally develop into bone, cartilage or other connective tissues including blood vessels, adipose (fat) tissue and smooth muscle. They can also develop from fibroblasts, cells that help to build the extra cellular matrix that keeps cells in their designated structures throughout the body.
In the central nervous system (CNS) the most common cells for these tumours to develop from are the pericyte cells that surround the capillaries (blood vessels) that irrigate the meninges, the membrane that surrounds the brain and spinal cord.
What grades of haemangiopericytoma/solitary fibrous tumour (HPC-SFT) appear within the brain and spine?
HPC-SFTs within the CNS are currently graded according to a three-tiered system, but some researchers consider there to be considerable overlap or signs of transition between the grades, leading them to believe that they are on a continuum rather than three distinct tumours.
Grade 1 haemangiopericytoma/solitary fibrous tumour (HPC-SFT)
Grade 1 HPC-SFT is classified as having a SFT phenotype (looking like a solitary fibrous tumour under a microscope) and is considered to be a benign tumour.
Grade 2 haemangiopericytoma/solitary fibrous tumour (HPC-SFT)
Grade 2 HPC-SFT is classified as having an HPC phenotype (looking like a haemangiopericytoma under a microscope). It is classified as a malignant tumour and requires radiotherapy in addition to neurosurgery in order to avoid recurrence and spread.
Grade 3 haemangiopericytoma/solitary fibrous tumour (HPC-SFT)
Grade 3 HPC-SFT is classified as having an HPC phenotype (looking like a haemangiopericytoma under a microscope). It is classified as a malignant tumour and requires radiotherapy in addition to neurosurgery in order to avoid recurrence and spread.
Are haemangiopericytoma/solitary fibrous tumours (HPC-SFT) benign or cancerous?
Grade 1 is generally considered to be a benign tumour, whilst grades 2 and 3 fall into the category of a faster-growing, more aggressive form of cancer.
Grades 2 and 3 are most likely to recur after treatment, and may sometimes spread (metastasise) to other parts of the body. Most commonly these are the lungs, liver or bones but one research paper also reported a metastasis into a kidney.
What is the prognosis for haemangiopericytoma/solitary fibrous tumour (HPC-SFT)?
Exact prognosis statistics are hard to establish due to the rarity of these tumours, and because the classifications have changed over time.
Prognosis is often good, especially for grade 1 tumours that can be fully removed by neurosurgery, as this treatment alone can result in a cure for many patients.
Higher grades and tumours unable to be completely removed by neurosurgery have a tendency to recur in more than 75% patients, and hold the possibility of spreading elsewhere in the body.
Whilst the majority of patients have tumours that remain within the brain and spine, up to 28% of HPC-SFT metastasise (spread) to sites outside the CNS. The most common sites for metastatic tumours are non-specified locations in the bone (19.6%), followed by lung and pleura (18.4%), liver (17.6%), and vertebrae of the spine (14.1%). Being diagnosed with a grade 2 or 3 HPC-SFT increases the chances of this happening, but location and treatment of the primary tumour, local recurrence and gender do not.
Metastases can occur in any age group and can be found within three months of diagnosis, or much later. They are typically diagnosed following symptomatic presentation, which is why long-term monitoring using regular scans is crucial for these patients.
No overall prognosis for HPC-SFT tumours is available due to their rarity and the wide range of survival times, influenced by any metastases and their outcomes.
What are the symptoms of a haemangiopericytoma/solitary fibrous tumour (HPC-SFT)?
The symptoms will depend upon exactly where the tumour is in the brain, and hence which parts of brain function are affected. Symptoms are likely to include one of more of the following:
- Changes in vision, such as seeing double or blurriness
- Headaches that worsen with time
- Hearing loss or ringing in the ears
- Memory loss
- Loss of smell
- Weakness in the arms or legs
How is a haemangiopericytoma/solitary fibrous tumour (HPC-SFT) diagnosed?
The most reliable way to diagnose any kind of brain tumour is initially by an MRI scan and then by taking a biopsy (a small sample of the tumour, removed during neurosurgery) for analysis in a laboratory.
How common are haemangiopericytoma/solitary fibrous tumours (HPC-SFT)? ?
These are very rare tumours, accounting for less than 1% of all primary CNS tumours.
Some studies report that HPC-SFT are most commonly diagnosed in young adults, but cases have been reported in children as young as three years old and adults up to 77 years old.
What causes a haemangiopericytoma/solitary fibrous tumour (HPC-SFT)?
The cause of most haemangiopericytoma / solitary fibrous tumours (HPC-SFT) is not known, so unfortunately there are no proven ways to prevent them from occurring.
Treatment options for haemangiopericytoma/solitary fibrous tumour (HPC-SFT)
The first type of treatment offered to patients would be neurosurgery, and in many cases a complete resection (removal) of a grade 1 HPC-SFT tumour that results in a cure can be achieved.
If some of the tumour is unable to be removed using neurosurgery, radiotherapy may also be offered.
Due to the risk of tumours developing in other parts of the body, regular long-term monitoring using Dotatate PET/CT scans is recommended.
There are many researchers looking for a cure for brain tumours, so new treatments may be available to some patients in the context of clinical trials.
How will we find a cure for haemangiopericytoma/solitary fibrous tumour (HPC-SFT)?
Research we are funding across all of our dedicated Research Centres will help lead towards finding a cure for a wide range of brain tumours.
Pioneering research at our Brain Tumour Research Centre at Queen Mary University of London is focused on using glioblastoma multiforme (GBM) stem cells to help develop unique, patient-specific treatments. GBMs are the most aggressive type of glioma brain tumour in adults. Findings are expected to translate into other types of adult and paediatric brain tumours.
Our team at the University of Plymouth Brain Tumour Research Centre are researching a number of molecular pathways that influence immune system function, tumour metabolism and tumour growth in a range of low-grade brain tumours in children and adults. This includes how gliomas begin, and how they transform from low-grade to high-grade.
The team of research and clinical experts in our Research Centre at Imperial College, London are studying the way in which the ketogenic diet works in brain tumours including DIPG. Their work on drugs that reduce levels of arginine, an amino acid in the blood, may also have the potential to influence a wide range of brain tumours.
We also fund BRAIN UK at Southampton University, the country’s only national tissue bank registry providing crucial access to brain tumour samples for researchers from all clinical neuroscience centres in the UK, effectively covering about 90% of the UK population, and an essential component in the fight to find a cure for all types of brain tumours.